Rastering laser scanner with beam location feedback

Abstract

A method and apparatus is provided for reading two-dimensional patterns, such as matrix symbols or signatures, using moving beam laser scanners to take advantage of the large depth of field inherent in laser scanners. A pixel generating element and a tracking element together create a digitized image of a target symbol by scanning a laser beam across the symbol. As the pixel generating element generates pixel data composing the digitized image, the tracking element tracks the position of the laser beam in the scanning pattern, and generates laser position data indicating the instantaneous position of the laser associated with particular pixels. The laser position data is then stored in a data memory in association with the generated pixel data, and a microprocessor utilizes the stored pixel data and laser position data to create an image of the target symbol.

What is claimed is: 
     
       1. A laser scanning apparatus comprising: a window;   means for scanning laser light in a two-dimensional pattern through said window and onto a target area; and   means for determining an instantaneous position of said laser light along said window at a point which said laser light passes through said window.   
     
     
       2. A laser scanning apparatus comprising: a window;   means for scanning laser light through said window and onto a target area; and   means for determining an instantaneous position of said laser light as said laser light passes through said window, wherein said determining means comprises an array of photodiodes oriented to permit a portion of said laser light that reflects off of said window to impinge thereon.   
     
     
       3. A laser scanning apparatus comprising: a window;   means for scanning laser light through said window and onto a target area; and   means for determining an instantaneous position of said laser light as said laser light passes through said window, wherein said determining means comprises at least one array of photodiodes disposed along at least one boundary of said window.   
     
     
       4. A laser scanning apparatus comprising: a window;   means for scanning laser light through said window and onto a target area; and   means for determining an instantaneous position of said laser light as said laser light passes through said window, wherein said determining means comprises a plurality of spaced apart photosensitive electrical conductors disposed in parallel to a plane of said window.   
     
     
       5. The apparatus of claim 1, wherein said scanning means comprises at least one movable mirror, and at least one motor for moving said at least one movable mirror. 
     
     
       6. The apparatus of claim 1, wherein said scanning means comprises: a first mirror movable in a first direction; and   a second mirror movable in a second direction.   
     
     
       7. The apparatus of claim 1, wherein said pattern is a raster pattern. 
     
     
       8. The apparatus of claim 1 further comprising: means for receiving laser light that has passed though said window and reflected off of said target area; and   means for generating digitized image data of said target area utilizing said received light.   
     
     
       9. The apparatus of claim 8 further comprising memory means for storing said position determined by said determining means. 
     
     
       10. The apparatus of claim 9, wherein said memory means further stores said position determined by said determining means in association with said image data generated by said generating means. 
     
     
       11. A laser scanning method comprising: scanning laser light in a two-dimensional pattern through a window and onto a target area; and   determining an instantaneous position of said laser light along said window at a point which said laser light passes through said window.   
     
     
       12. The method of claim 11, wherein said pattern is a raster pattern. 
     
     
       13. The method of claim 11 further comprising: receiving laser light that has passed though said window and reflected off of said target area; and   generating a digitized image of said target area utilizing said received light.   
     
     
       14. The method of claim 11 further comprising storing said position determined at said determining step. 
     
     
       15. The method of claim 14, wherein said storing step further stores said position determined at said determining step in association with said image data generated at said generating step. 
     
     
       16. An apparatus comprising: a window;   a movable mirror disposed so as to reflect laser light through said window and onto a target area;   a motor movably connected to said movable mirror so as to move said movable mirror to cause said laser light to sweep through a two-dimensional pattern; and   means for determining a position of said laser light along said window at a point which said laser light passes through said window.   
     
     
       17. An apparatus for forming a two-dimensional image, comprising: a laser light emitter adapted to emit a beam of laser light and means for sweeping said laser light beam through a two-dimensional pattern;   a detector oriented to detect an instantaneous position of said laser light beam as said laser light beam sweeps through said pattern to provide position data;   an imaging sensor oriented to receive said laser light beam after having reflected off of a target surface area to provide image data; and   means for correlating said position data with said image data to reconstruct a two-dimensional image of said target surface area.   
     
     
       18. The apparatus of claim 17, wherein said target surface area further comprises a two-dimensional bar code symbol. 
     
     
       19. The apparatus of claim 17, wherein said detector further comprises: a window oriented to permit said sweeping laser light beam to pass therethrough; and   at least one array of photodiodes oriented with respect to said window to permit a portion of said laser light beam to impinge thereon.   
     
     
       20. The apparatus of claim 19, wherein said at least one array of photodiodes are disposed along at least one boundary of said window. 
     
     
       21. The apparatus of claim 17, wherein said detector further comprises: a window oriented to permit said sweeping laser light beam to pass therethrough; and   a plurality of spaced apart photosensitive electrical conductors disposed in parallel to a plane of said window and oriented to permit a portion of said laser light beam to impinge thereon.   
     
     
       22. The apparatus of claim 17, wherein said two-dimensional pattern further comprises a raster pattern. 
     
     
       23. A method for forming a two-dimensional image, comprising the steps of: emitting a beam of laser light and sweeping said laser light beam through a two-dimensional pattern;   detecting an instantaneous position of said laser light beam as said laser light beam sweeps through said pattern to provide position data;   receiving said laser light beam after having reflected off of a target surface area to provide image data; and   correlating said position data with said image data to reconstruct a two-dimensional image of said target surface area.   
     
     
       24. The method of claim 23, wherein said detecting step further comprises the steps of: passing said laser light beam through a window; and   detecting instantaneous points at which said laser light beam passes through said window.